1. Field of the Invention
The present invention relates to a measurement apparatus, an information obtaining apparatus, and a measurement method for measuring a time waveform of a terahertz wave by using time-domain spectroscopy.
2. Description of the Related Art
Terahertz waves typically are electromagnetic waves having components of a certain frequency band within the range of 0.03 THz to 30 THz. There is terahertz time-domain spectroscopy (THz-TDS) available as spectroscopy using such terahertz waves. This is a method in which a time waveform of a terahertz wave is obtained by detecting the terahertz wave while changing the timing at which pump light output from a light source reaches a generating unit or the timing at which probe light reaches a detecting unit. With the adjustment of the timing, the timing at which the probe light and a terahertz wave enter the detecting unit is adjusted, and the terahertz wave is measured through sampling by using the probe light.
In a measurement apparatus using the principle of the THz-TDS method (THz-TDS apparatus), it is important to reduce an influence of vibration or the like generated by an external factor, in order to accurately obtain a time waveform. Specifically, it is required to suppress the occurrence of a situation in which an external factor that acts on an optical system of the measurement apparatus causes the optical system to vibrate, and the vibration affects a time waveform to be obtained.
Japanese Patent Laid-Open No. 2007-240191 discloses a configuration in which obtainment of a time waveform is deferred for a certain period of time in a case where vibration from an apparatus placed outside a measurement apparatus is detected.
In the method disclosed in Japanese Patent Laid-Open No. 2007-240191, obtainment of a time waveform is deferred for a certain period of time even after vibration has converged in some cases. Such an unnecessary waiting time makes it difficult to shorten the period of time required to obtain a time waveform.